Ultra high resolution, low temperature, direct metal patterning by selective laser processing of solution deposited meta
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1247-C09-05
Ultra high resolution, low temperature, direct metal patterning by selective laser processing of solution deposited metal nanoparticles Seung H. Ko1,2*, DongYeol Yang2, Heng Pan2, Jean M. Frechet3, Yong Son1, Tae Woo Lim1, Junyeob Yeo1, Costas. P. Grigoropoulos1 1 Applied Nano Tech & Science lab, KAIST, Daejeon, Korea. 2 Laser Thermal Lab, University of California, Berkeley, California 94720-1740, USA. 3 Chemistry Dept., University of California, Berkeley, California 94720-1740, USA. ABSTRACT All-printed electronics is the key technology to ultra-low-cost, large-area electronics. As a critical step in this direction, we demonstrate that femtosecond laser processing (sintering and ablation) of solution deposited metal nanoparticles enables direct metal patterning at lowtemperature with ultra high resolution (~300nm) to overcome the resolution limitation of the current inkjet direct writing processes. This could be explained by the combined effects of novel properties of metal nanoparticles such as melting temperature drop, strong absorption of the incident laser beam at surface plasmon mode, lower conductive heat transfer loss, and the relatively weak bonding between nanoparticles. Local thermal control of the laser sintering process could minimize the heat-affected zone and the thermal damage to the substrate and further enhance the resolution of the process. This local nanoparticle deposition and energy coupling enable an environmentally friendly and cost-effective process as well as a low-temperature manufacturing sequence to realize large-area, flexible electronics on polymer substrates. INTRODUCTION The electric circuit fabrication on a polymer substrate has gained significant interest as a pathway to low cost or large area electronics. [1,2] The conventional vacuum deposition and photolithographic patterning methods are well developed for inorganic microelectronics. However, flexible polymer substrates are chemically incompatible with resists, etchants and developers used in conventional IC processing. In practice, conventional IC fabrication processes are subject to limitations, in that they are multi-step, involve high processing temperatures, toxic waste and are therefore expensive. Furthermore, the increasing size of electronic devices such as displays poses great difficulty in adapting standard microfabrication processes, including lithographic patterning. The high resolution direct printing technique is of particular interest as an alternative to conventional vacuum deposition and photolithographic patterning of various functional films such as gate electrodes, gate dielectrics, source and drain contacts, and active semiconductor layers. [1] Among direct printing techniques such as micro contact printing (μ-CP) [1,3-4], thermal imaging [5], solid state embossing [6], screen printing [7,8], drop-on-demand (DOD) inkjet printing [9-12,15-19] and laser induced forward transfer (LIFT)[13-14], inkjet direct writing has emerged as an attractive direct patterning technique. This is chiefly because th
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